1. Field of the Invention
The present invention relates to a lens barrel equipped with a lens holding frame with circumferentially arranged cams. The present invention also relates to a camera system and a camera.
2. Related Background Art
Recently, the automatic focusing system has come into general use in interchangeable lens systems for single-lens reflex cameras, and apparatuses having a lens driving actuator inside the lens barrel thereof are becoming increasingly common.
As a result of the recent demand for portability, single-lens reflex cameras have been substantially reduced in size, and a further reduction in the size of the lens barrel is required even in the case in which the lens barrel contains the lens driving actuator. Further, along with the further reduction in size, there is a demand for a further increase in power in the case of a zoom lens.
A conventional lens barrel will be briefly described with reference to FIG. 6, which is a sectional view. In the case of this lens barrel, a lens driving actuator 30 is arranged in the outer periphery of a cam barrel 31 for causing a lens holding frame to advance or retreat along an optical axis direction of the lens. In some cases, however, not limited to the example described above, the lens driving actuator 30 is arranged in the vicinity of the rear end of the cam barrel 31 with respect to the optical axis direction. An example of such conventional lens barrels is disclosed in Japanese Patent Application Laid-Open No. H06-174997.
In such conventional examples as described above, however, there is a fear of the maximum lens diameter or the total barrel length becoming rather large.
Recently, the digitization of single-lens reflex cameras has also progressed, and there is a demand for a further improvement in optical performance so that a user of the camera can easily obtain an enlarged photographic image by using a personal computer or the like. The improvement in optical performance involves enhanced optical sensitivity, so that there is also a need for an improvement in terms of accuracy with respect to offset and inclination due to play in the lens holding frame in the lens barrel.